1. Field of Invention
The present invention relates generally to the field of wireless communication and networks. More particularly, in one exemplary aspect, the present invention is directed to methods and apparatus for providing various levels of access to a femtocell or other network resource operating within a public network.
2. Description of Related Technology
The Universal Mobile Telecommunications System (UMTS) is an exemplary implementation of a “third-generation” or “3G” cellular telephone technology. The UMTS standard is specified by a collaborative body referred to as the 3rd Generation Partnership Project (3GPP). The 3GPP has adopted UMTS as a 3G cellular radio system targeted for inter alia European markets, in response to requirements set forth by the International Telecommunications Union (ITU). The ITU standardizes and regulates international radio and telecommunications.
A current topic in the 3GPP standardization committees is the further development of 3G UMTS towards a mobile radio communication system optimized for packet data transmission by improving both system capacity and spectral efficiency. In 3GPP, the activities in this regard are summarized under the general term LTE (Long Term Evolution). The aim for this future technology is, among others, to significantly increase the maximum net transmission rate, namely to 100 Mbps in the downlink transmission direction (base station to cellular phone) and to 50 Mbps in the uplink transmission direction (cellular phone to base station). Various techniques have been specified to improve transmission via the air interface.
Multiple Input Multiple Output (MIMO) is one such technique proposed for LTE. MIMO is an antenna technology in which up to four (4) antennas (the maximum number of antennas specified for LTE) are used at both the base station and user terminal. MIMO supports multiple independent data streams transmitting in parallel using the same time-frequency resources. Spatial division multiplexing is applied to distinguish the data streams at the receiver (e.g. each path traverses a different path, and is susceptible to different channel effects).
Another technology utilized in UMTS (and most likely in future versions of LTE) is Multimedia Broadcast Multicast Services (MBMS). While MBMS is generally considered a downlink only service (akin to digital television), the MBMS infrastructure does enable uplink channels for interaction between the service provider and subscriber/user. Logically, MBMS uses multicast distribution in the Core Network (instead of point-to-point links for each end device), to efficiently distribute data. Multicast and broadcast distribution technologies may advantageously reuse radio resources (e.g. time slots, frequency bands, etc.), and Radio Resource Connections (RRC) to service multiple users. MBMS technology is described in greater detail subsequently herein.
In addition to radio technology research related to increasing capacity and bandwidth, 3GPP has also promoted the development of so-called “femtocell” technology. The cost of purchasing fixed base stations (BS, also known as “macrocells”) and their associated maintenance in a wireless network is comparatively high. Femtocells, on the other hand, are smaller more inexpensive cellular base stations purchased by a home, small office, or other premises user. Network providers may even subsidize the cost of a femtocell to such users, thereby making them more attractive to the user from a financial perspective.
A femtocell augments the service provider's existing network of base stations by connecting to the service provider's network via a broadband interface (such as DSL, T1, ISDN, or DOCSIS cable modem). Due to the smaller size and lower cost of a femtocell, they can be utilized in areas which are otherwise not feasibly serviced through standard base station deployments (e.g., by extension of indoor service coverage, or temporary service coverage). They also may be somewhat portable in nature, and accordingly be repositioned when desired with fairly minimal effort. Various aspects of femtocells are described in greater detail subsequently herein.
Currently, the standardization body for mobile communication (3GPP) is specifying a new network femtocell element known as “Home Node B” (HNB). A Home Base Station (or Home NodeB, or Home eNodeB in 3GPP terminology) is a femtocell optimized for use in residential, corporate, or similar environments (e.g., private homes, public restaurants, small offices, enterprises, hospitals, etc., and hence the term “home” is not meant to be limiting to residential applications). In the present context, the terms “Home Base Station”, “Home NodeB” (for UMTS), “Home eNodeB” (for LTE), and “femtocell” refer to the same logical entity, and are used interchangeably unless otherwise noted.
The 3GPP is currently researching possible solutions for supporting the deployment of HNBs for the following radio access technologies: 3G UMTS (UMTS solutions are based on CDMA and referred to as UMTS Terrestrial Radio Access (UTRA) in 3GPP terminology), and 3.9G LTE (Long Term Evolution solutions are referred to as Evolved-UTRA (E-UTRA) in 3GPP terminology).
In one exemplary usage case, a user of a mobile phone or other User Equipment (UE) might wish to augment their wireless coverage by deploying a HNB in their premises (e.g., apartment). In one scenario, the user employs a DSL or other such connection to connect the HNB to the operator's Core Network. The usage is beneficial for both operator and user; from the customer's perspective, HNBs offer the seamless operation of a single mobile handset with a built-in personal phonebook for all calls, whether at home or elsewhere. The user maintains only one contract and one bill with the service provider. The user also benefits from the improved indoor network coverage, as well as increased traffic throughput capabilities.
Furthermore, the user's mobile phone will have a longer standby battery life when the phone is used indigenously; power consumption can be reduced due to the improved radio link quality (i.e. improved Signal to Noise Ratio (SNR)) which can be expected to be better than that of the link between the handset and legacy ‘NodeB’ located farther (e.g., a few hundred meters or more) away.
The network operator also obtains additional network coverage area (see, e.g., 3GPP TR 25.820, “3G Home Node B Study Item Technical Report” v100 (Release 8), which is incorporated herein by reference in its entirety).
Finally, both the home user and the network operator can fully utilize cellular equipment technology improvements, independent of the larger network capabilities and requirements for infrastructure upgrade.
The simplicity of HNB operation for the home user creates some unique challenges for network operators. Prior to the deployment of femtocells, base station networks were planned and controlled entirely by the network operator. Network access functions such as security and authorization were easily controlled by a network operator through base station fixtures. However, the “randomized user distribution” of HNBs significantly complicates fixed base station network operations.
The “Closed Subscriber Group” (CSG) capability is one specific example of the new complexities introduced by HNB operation within existing UMTS cellular networks. Usually access to a HNB will be allowed for a closed user group; e.g., service offerings of a particular cell may be restricted to employees of a certain company, members of a given family, etc. The general concept of restricting service offerings of femtocells (and base stations) is termed Closed Subscriber Group Cells (CSG Cells) in the context of the 3GPP Standards. CSG technology is described in greater detail subsequently herein.
Closed Subscriber Groups are often a necessity to provide sufficient incentive home/small business users to at least partially subsidize the cost of new technologies, e.g. deployments of HNBs, etc. That is, a prospective HNB user will want “user exclusivity” in exchange for their financial and/or other contributions to setting up and operating the HNB. However, currently proposed implementations of CSG Cells in certain circumstances are overly restrictive, and may prove detrimental to overall network resources, especially with certain types of multimedia services, and/or service capabilities. For example, a UE denied HNB access to the desired (e.g., MBMS) service would then require allocation of network resources that would not otherwise have to be allocated were access to the HNB made less restrictive.
Therefore, greater flexibility in access control for use with heterogeneous access networks (e.g., having both public or “open”, and private or “closed” group access) is desirable for public cellular networks (e.g., UMTS/LTE) and femtocells (e.g., HNBs/eHNBs). Prior art solutions for cellular networks are not adequate when applied to the operation of closed cell groups within the network. Some solutions which have been implemented for other communications networks use localized methods for authentication and authorization; this may be undesirable for cellular network providers, which prefer to maintain a single global logical entity for such procedures. Furthermore, other solutions have required additional software or hardware (such as specialized identities or priority classes), which are also not desirable for femtocell usage, as they require interaction with the public network resources (such as to authorize validity of the user), in addition to private network resources (e.g., to evaluate the specialized identities/priority), thereby making the process unduly complex and burdensome.
Hence, improved solutions are needed to provide sufficient access control solutions for use within heterogeneous access networks, while still maintaining the benefits of exclusivity offered by CSG cell capabilities and leveraging femtocell flexibility. Such improved solutions would ideally operate within existing cellular networks without requiring significant software or hardware changes, and remain compatible with existing network infrastructure and currently serviced user equipment (UE); i.e., “backwards compatibility”.